Field of the Invention
The present invention relates to a cooling structure in an exhaust muffler for decreasing the amount of noise emitted by the exhaust gases of a combustion engine.
Description of Related Art
JP Laid-open Patent Publication No. H09-228836, for example, discloses an engine system including a cooling fan adapted to be driven in association with an engine rotary shaft so that an engine cylinder can be cooled by a cooling air or air, in which a portion of the cooling air from the cooling fan is guided to cool an outer surface of a muffler.
It has, however, been found that with the cooling structure disclosed in the JP Laid-open Patent Publication No. H09-228836 referred to above, difficulty has been found in guiding the cooling air efficiently over the entire outer surface of the muffler. It has also been found that mere cooling of the outer surface is far from sufficiently cooling the muffler to the deepest region of the interior thereof.